Parkinson's disease is a devastating, universally fatal, incurable neurodegenerative disorder, which is debilitating and inflicts terrible suffering on the patient's mind and body. Human pluripotent cells, including embryonic stem cells, have been identified as a potential alternative cellular substrate for treatment, but to date, have not been tested for long-term therapeutic efficacy in disease relevant animal models (MPTP lesioned monkeys). Our long-term goal is to assess the safety and temporal efficacy of HESC-DA cell therapy in PD patients. The current objective is to determine if grafted HESC-DA cells are a potent long-lasting therapy that structurally integrate within the dopamine depleted primate brain, as well as reverse functional deficits associated with PD. Our central hypothesis is that intrastriatal delivery of HESC-DA cells will reverse motor disability in MPTP treated monkeys and this effect will be potentiated by co-treating with AAV-neurturin. The rationale for the proposed research is if HESC-DA grafts ameliorate functional deficits in parkinsonian primates, we can pursue large-scale, long-term safety and tolerability studies as the next logical step for clinical translation. Guided by preliminary data, this hypothesis will test the following Specific Aim, that intrastriatal grafting of HESC-DA cells, or HESC-DA cells + AAV2-Neurturin will provide structural and functional recovery in MPTP monkeys. Utilizing a novel floor-plate based, dopaminergic neuralization paradigm that allows HESC to be efficiently differentiated into midbrain specific dopaminergic neurons, and we will determine the effects of grafted HESC-DA cells on host anatomical structure and function and correlate these results to overall quality of life (clinical rating scale). In the proposed Aim, immunohistochemical analysis and behavioral testing will be used to complement in vivo imaging in an effort to bridge a critical gap in knowledge for PD therapeutics. This research is innovative, as it 1) focuses on well characterized, functionally active, midbrain specific HESC- DA neurons as an alternative renewable source for cellular transplantation 2) advances our knowledge of the functional efficacy of this approach by utilizing a clinically relevant non-human primate model of PD, and 3) vertically advances and bridges our present studies with the addition of AAV-2 neurturin neurotrophic support. This proposal is significant as rigorously testing HESC-DA therapies in parkinsonian monkeys more accurately depicts human PD, and therefore, the proposed experiments are more likely to provide quality translatable results to the clinic. The outcomes are expected to vertically advance the field of PD therapy through the blending of neurosurgery and stem cell biology. The knowledge obtained here has the potential to provide a therapeutic option that will reduce the terrible symptoms and enhance overall quality of life in PD.